Problem: What is the amplitude of $y=3\sin(2x-1)+4$ ?
Explanation: Amplitude in sinusoids of the form $y=a\sin(bx+c)+d$ The amplitude of a sinusoid of the form $y={a}\sin(bx + c) + d$ is equal to $|{a}|$. [How can we justify this given our graphical understanding of amplitude?] Finding the amplitude The amplitude of $y = {3}\sin(2x-1)+4$ is $|{3}|=3$.